The YA novel The Fandom (Chicken House/Scholastic, 2018) by Anna Day reminds me a bit of The Inn Between for middle grade readers–things are not always what you think. It was a compelling read, too.
Seventeen-year-old Violet, two girlfriends, and her fourteen-year-old brother are at Comic-Con to meet the actors from The Gallows Dance. A strange accident transports them into the universe where the real people from the story live. Was the book (and movie) based on this universe, or birthed out of the book? They don’t know, but all their lives are in danger. Especially if they can’t get back home.
This is the author’s debut book and was first published in the UK. If you don’t want to read the whole long version “About Anna,” definitely read the last paragraph.